1. Field of the Invention
The present invention relates to a laminated ceramic electronic component used for an electronic device.
2. Background Art
In recent years, a demand has been increasing for higher performance, downsizing, and thickness reduction in electronic devices as represented by a mobile communication device. Following this, a demand has been increasing for higher density and higher performance in electronic components as well. Consequently, when mounting electronic components on a printed wiring board, higher density is required while reducing the number of electronic components mounted on the surface of a printed wiring board for downsizing. For this purpose, development has been made of a component-embedded printed wiring board structured to include electronic components in the board.
Laminated ceramic electronic components used for a component-embedded printed wiring board include a laminated ceramic capacitor and a laminated varistor. A laminated ceramic capacitor, for example, is demanded that is small-size, slim, and large-capacitance with a length of 1.0 mm; width, 0.5 mm; and thickness, 0.1 mm to 0.5 mm.
FIG. 7 is a sectional view of a conventional component-embedded printed wiring board. FIG. 8 is a sectional view of a conventional laminated ceramic capacitor. As shown in FIG. 7, component-embedded printed wiring board (wiring board, hereinafter) 31 includes insulative resin layer 32, laminated ceramic capacitor (capacitor, hereinafter) 40, and wiring pattern 35. Insulative resin layer 32 made of such as a glass epoxy resin has interlayer connection hole 33 vertically provided therein. Capacitor 40 is electrically connected to wiring pattern 35 through interlayer connection hole 33. Conductor junction 34 is formed in interlayer connection hole 33, made of a metal layer formed by such as plating or of such as a conductive paste filler.
As shown in FIG. 8, capacitor 40 includes laminated ceramic element 43 and external electrodes 44. Laminated ceramic element 43 is formed of internal electrode layers 42 and ceramic layers 41 alternately laminated. External electrodes 44 continuous with internal electrode layer 42 are disposed at both ends of laminated ceramic element 43. As shown in FIG. 7, a part of external electrode 44 formed on main face 47 is joined to conductor junction 34.
External electrode 44 is composed of base electrode layer 45 and metal layer 46. Base electrode layer 45 is formed by applying the end of laminated ceramic element 43 with a conductive paste by dip coating and then baking the paste. Metal layer 46 is formed by plating base electrode layer 45.
In capacitor 40, namely a conventional laminated ceramic electronic component, the part of external electrode 44 on main face 47 is joined to conductor junction 34. Consequently, the part requires an area larger than that of conductor junction 34. This is to retain electrical bonding and bonding strength with conductor junction 34 to ensure the reliability of bonding. Prolonging external electrode 44 on main face 47 to ensure the bonding area results in thick external electrode 44 formed by dip coating due to the viscosity of the conductive paste. For this reason, to implement thinness required in capacitor 40, the thickness of entire laminated ceramic element 43 needs to be reduced. In this case, the number of lamination of ceramic layers 41 and internal electrode layers 42 needs to be reduced, thereby decreasing the capacitance of capacitor 40.